Systems, Apparatuses, and Methods for Removal and Insertion of Thrusters using a Transfer System

ABSTRACT

Embodiments of the present disclosure include apparatuses and methods for the underwater removal and insertion of thrusters using a transfer system. Embodiments include a transfer system having a deck fitting assembly configured to be mounted to a hull of a marine vessel, a tension rod assembly secured to the deck fitting assembly, a track system secured to the tension rod assembly, a transfer frame movably secured to the track system via a hoist system, and a cradle removably secured to the transfer frame. Cradle and transfer frame are vertically movable and horizontally traversable along a portion of the hull via the hoist system.

This application claims the benefit of U.S. Provisional PatentApplication No. 62/091,338, filed on Dec. 12, 2014, which isincorporated herein by reference.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a transfer system attached to a frontportion of a hull with a cradle being lowered onto a transfer frame,according to an exemplary embodiment of the present disclosure.

FIG. 2 is an isometric view of the transfer system shown in FIG. 1 afterinsertion of the cradle onto the transfer frame, according to anexemplary embodiment of the present disclosure.

FIG. 3 is a bottom isometric view of the transfer system shown in FIG. 1without the cradle, according to an exemplary embodiment of the presentdisclosure.

FIG. 4 is a bottom isometric close-up view of a thruster well openingunder the hull shown in FIG. 3.

FIG. 5 is an isometric close-up view of tension rod assemblies installedon the side of a hull using deck fitting assemblies, according to anexemplary embodiment of the present disclosure.

FIG. 6 is a top view of a transfer system with long and short deckfitting assemblies attached to sides of the hull shown in FIG. 1.

FIGS. 6A and 6B are close-up top views of the long and short deckfitting assemblies shown in FIG. 6 with support flanges installed.

FIGS. 6C and 6D are close-up top views of the long and short deckfitting assemblies shown in FIG. 6 without support flanges installed.

FIGS. 7A and 7B are front and side views of a tension rod assemblyinstalled on the side of a hull, according to an exemplary embodiment ofthe present disclosure.

FIGS. 7C, 7D, and 7E are additional fragmentary enlarged views of partsof the tension rod assembly shown in FIGS. 7A and 7B.

FIG. 7F is an isometric close-up view of the tension rod assembly shownin FIGS. 7A and 7B attached to a track system, according to an exemplaryembodiment of the present disclosure.

FIG. 7G is a side close-up view of a hydraulic pre-tensioning ramattached to the tension rod assembly shown in FIGS. 7A and 7B, accordingto an exemplary embodiment of the present disclosure.

FIGS. 8A and 8B are top and bottom isometric views, respectively, of atrack system, according to an exemplary embodiment of the presentdisclosure.

FIG. 9 is an isometric view of a transfer frame, according to anexemplary embodiment of the present disclosure.

FIGS. 10A, 10B, and 10C are front, side, and top views, respectively, ofa hoist system in a retracted position, according to an exemplaryembodiment of the present disclosure.

FIGS. 10D, 10E, 10F, and 10G are front, side, and bottom isometricviews, respectively, of a hoist system in an extended position,according to an exemplary embodiment of the present disclosure.

FIGS. 11A and 11B are bottom isometric and side views, respectively, ofa hoist system, according to an exemplary embodiment of the presentdisclosure.

FIG. 12 is a top isometric view of a transfer frame attached to a tracksystem via a hoist system, according to an exemplary embodiment of thepresent disclosure.

FIG. 13 is an isometric view of a cradle, according to an exemplaryembodiment of the present disclosure.

FIGS. 13A, 13B, 13C, and 13D are additional fragmentary enlarged viewsof parts of the cradle shown in FIG. 13.

FIG. 14 is an isometric view of a carriage assembly, according to anexemplary embodiment of the present disclosure.

FIG. 15 is a bottom isometric view of the carriage assembly shown inFIG. 14 positioned under a thruster well opening in an extendedposition, according to an exemplary embodiment of the presentdisclosure.

FIG. 16 is a bottom isometric view of the carriage assembly shown inFIG. 15 raised to a retracted position towards the thruster wellopening, according to an exemplary embodiment of the present disclosure.

FIG. 17 is a bottom isometric view of a thruster being lowered into thecarriage shown in FIG. 16, according to an exemplary embodiment of thepresent disclosure.

FIG. 18 is a bottom isometric view of the carriage and enclosed thrustershown in FIG. 17 being lowered into an extended position, according toan exemplary embodiment of the present disclosure.

FIG. 19 is a bottom isometric view of the carriage and enclosed thrustershown in FIG. 18 positioned at an end of the track system, according toan exemplary embodiment of the present disclosure.

FIG. 20 is an isometric view of a cradle and enclosed thruster beingraised from a transfer system attached to a hull, according to anexemplary embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Current vessel thruster maintenance is inefficient and costly. Thrustermaintenance may be done while a vessel is dry docked or in water. Bothof these options present several disadvantages. First, thrustermaintenance performed at a dry dock requires the use of expensive dockspace that includes using large tracts of ocean front real estate andhighly customized equipment. Additionally, thruster maintenanceperformed at a dry dock results in lost vessel operating time. Removaland repair of a thruster in water can be difficult and dangerous forthose attempting to perform the removal and repair. Systems performingunderwater removal and repair of thrusters have involved the use ofunderwater divers manually moving the thruster out of a thrusterchannel, and then attaching cables to raise the thruster to the watersurface.

Apparatuses and methods for mounting and dismounting thrusters to andfrom the hull of a vessel are disclosed in U.S. Pat. Nos. 4,066,034,4,066,035, and WIPO Patent Application No. WO 2014/091063, which areincorporated herein by reference. U.S. Pat. Nos. 4,066,034 and 4,066,035disclose mounting and dismounting using a plurality of cables suspendedfrom a crane or other similar lifting/lowering device. WIPO PatentApplication No. WO 2014/091063 discloses mounting and dismounting usinglifting wires and crane wires connected to a supporting cradlecontaining the thruster unit. Divers are used to fasten and loosen thecrane wires and lifting wires. Utilizing lifting wires and/or cablesplace the divers (and thrusters) at risk because they may lead tounbalancing or unhinging of the thruster while being manually moved andraised to the water surface with the attached cables, or even worse,breaking of the cables when raising the thrusters—a potentiallylife-threatening situation for the divers. Additionally, due to theirparticular size and construction, cranes and/or similar systems can onlyperform mounting and dismounting of thrusters in deep waters furtheroffshore (i.e. not in shallow waters), leading to additional costs andinefficiencies in thruster operation.

Embodiments of the present disclosure relate to transfer systems,apparatuses, and methods, and in particular though non-limitingembodiments, to systems, apparatuses, and methods for the removal andreinsertion of thrusters from a hull using a transfer system.

Embodiments provide apparatuses and methods for the underwater removaland insertion of thrusters using a transfer system. Embodiments includea transfer system having deck fitting assemblies configured to bemounted to a hull of a marine vessel, tension rod assemblies secured tothe deck fitting assemblies, a track system secured to the hull by thetension rod assemblies, a transfer frame movably secured to the tracksystem via a hoist system, and a cradle removably secured to thetransfer frame. The cradle and transfer frame may be collectivelyreferred to herein as a “carriage” or “carriage assembly.” The carriagemay be vertically movable and horizontally traversable along a portionof the hull.

Embodiments provide methods for removing, and subsequently reinserting,a thruster from, and into, a thruster well opening under a hull of amarine vessel using the transfer system described herein. According toan exemplary embodiment, a method includes installing the transfersystem on the hull, moving the carriage across the track system towardsa position directly under an opening of the hull via a hoist system,raising the carriage towards the opening via the hoist system, loweringthe thruster from inside the hull through the opening and into thecarriage, lowering the carriage and enclosed thruster away from theopening via the hoist system, moving the carriage and enclosed thrusteracross the track system towards an end of the track system, and removingthe cradle and enclosed thruster from the transfer system. Once thethruster is removed and repaired/replaced, the method further includeslowering the cradle and enclosed repaired/new thruster onto the transferframe, moving the carriage and enclosed thruster across the track systemtowards the position directly under the opening of the hull via thehoist system, raising the carriage and enclosed thruster towards theopening via the hoist system, and raising the thruster from the carriagetowards and into the opening.

Embodiments of the present disclosure can take several forms and may beused with various different marine vessels. In instances, the marinevessel may be a cargo, container, or tanker ship. In other embodiments,the marine vessel may be a remote drilling or space launch platform,submarine, warship, tug, or any other vessel that utilizes underwaterthrusters. The present disclosure may be used to remove and replacevarious different types of objects/equipment from the bottom of avessel, including various types of thrusters. In example embodiments,thrusters may be any commercially available azimuth thrusters or tunnelthrusters from suppliers such as Wärtsilä®, Rolls-Royce®, or MassonMarine.

Embodiments of the present disclosure allow for the safe and efficientmounting and dismounting of thrusters from vessels in shallow watersusing the transfer system described herein. Doing so is in shallowwaters is an improvement over existing crane systems that can onlyperform mounting and dismounting in deep waters.

Turning to FIG. 1, a transfer system 100 is shown. The transfer system100 includes deck fitting assemblies 102 configured to be mounted to asurface of a hull 101, tension rod assemblies 200 secured to the deckfitting assemblies 102, a track system 300 secured to the hull 101 bythe tension rod assemblies 200, a transfer frame 500 movably secured tothe track system 300 via a hoist system 400, and a cradle 600 removablysecured to the transfer frame 500. In an exemplary embodiment, thetransfer system 100 includes two tension rod assemblies 200 secured totwo deck fitting assemblies 102, respectively, on each opposing side ofthe hull 101. As shown in FIG. 1, the cradle 600 is lowered down alongdirection A. Cradle 600 may be lowered via any known lifting and/orlowering device, including a crane. Once fully lowered, the cradle 600fits snugly on the transfer frame 500. FIG. 2 is an isometric view ofthe cradle-transfer frame structure, also referred to as acarriage/carriage assembly 650. In embodiments, the carriage 650 ismovable along multiple axes. Particularly, the carriage 650 isvertically movable, and also horizontally traversable along an undersideportion of the hull 101 across track system 300. As seen in FIG. 2, thecarriage 650 is horizontally movable in the direction, B. FIG. 3 is abottom isometric view of the transfer frame 500 attached to track system300 installed under the hull 101. As shown, the bottom of the hull 101includes a thruster well opening, O, for removal and insertion of athruster. FIG. 4 is a bottom isometric close-up view of opening, O. Oncethe carriage 650 is moved along the track system 300 in the direction,B, towards a position directly under opening, O, the carriage 650 israised towards opening, O, to facilitate removal and insertion of athruster.

FIG. 5 is an isometric close-up view of tension rod assemblies 200installed on the side of a hull 101 using deck fitting assemblies 102.Each deck fitting assembly 102 includes a deck block 103 mounted onto adeck plate 105 and a support flange 104 installed onto the deck block103. Support flange 104 is configured to support and attach tension rodassembly 200 to a side of hull 101. In exemplary embodiments, deck block103 is welded to deck plate 105. However, any other attachmentmechanisms may be used to attach deck block 103 to deck plate 105. Deckblock 103 includes a plurality of holes/openings 103 a configured suchthat the support flange 104 may be easily adjustable along differentpositions on the deck block 103, thereby allowing for pure verticalalignment of a tension rod assembly 200 with reference to a track system300 installed under the side of a hull. See, e.g., FIGS. 1 and 2.

Deck fitting assemblies 102 may be long 102 a and/or short 102 b deckfitting assemblies 102. FIG. 6 is a top view of a transfer system withlong and short deck fitting assemblies 102 a, 102 b attached to sides ofa hull 101. FIGS. 6A and 6B are close-up top views of the long and shortdeck fitting assemblies 102 a, 102 b with support flanges 104 installed.FIGS. 6C and 6D are close-up top views of long and short deck fittingassemblies 102 a, 102 b without support flanges 104 installed. Inexemplary embodiments, the long deck fitting assembly 102 a is installedon a side of the hull 101 supporting a cradle 600 and/or thruster, andthe short deck fitting assembly 102 b is installed on an opposing sideof the hull 101. As shown in FIG. 6C, the long deck fitting assembly 102a includes a deck block 103 positioned on a center of the deck plate 105to account for installation of a long support flange 104. Long supportflange 104 may be attached onto deck block 103 via nuts and/or bolts orother attachment mechanisms. In exemplary embodiments, the long supportflange 104 and a tension rod assembly 200 are installed onto the deckblock 103 by screwing/inserting a torque heavy duty hex nut 104 a, aswell as a bolt 104 b. See FIG. 6A. As shown in FIG. 6D, the short deckfitting assembly 102 b includes a deck block 103 positioned on anend-facing side of the deck plate 105 to account for installation of ashort support flange 104. Short support flange 104 may be attached ontodeck block 103 via nuts and/or bolts or other similar attachmentmechanisms. In exemplary embodiments, the short support flange 104 and atension rod assembly 200 are installed onto the deck block 103 byscrewing/inserting a torque heavy duty hex nut 104 a, as well as a bolt104 b. See FIG. 6B. In exemplary embodiments, hex nut 104 a of long andshort deck fitting assemblies 102 a, 102 b is capable of achieving apreload of 32,000 lbs to meet a 66,000 lb payload limit. Bolt 104 b maybe a 1¼″ diameter bolt. Bolt 104 b may be tightened to 1400-1500 ft-lbsof torque tension.

Turning to FIGS. 7A and 7B, front and side views of a tension rodassembly 200 installed on the side of a hull 101 are shown. FIGS. 7C,7D, and 7E are additional fragmentary enlarged views of parts of thetension rod assembly 200 shown in FIGS. 7A and 7B. FIG. 7F is anisometric close-up view of tension rod assembly 200 attached to a tracksystem 300. Tension rod assembly 200 is configured to attach to andsecurely hold in place a track system 300 underneath a hull 101. Inexemplary embodiments, two tension rod assemblies 200 are used on eachopposing side of a hull 101. See, e.g., FIG. 1; FIG. 6.

Tension rod assembly 200 includes three tension rods 201 a 201 b 201 cremovably secured to each other. See FIGS. 7A and 7B. Link plate 204 isused to secure tension rod 201 a to tension rod 201 b via upper clevisfastener 202 and lower clevis fastener 203. A clevis is a U-shaped orforked metal connector within which another part can be fastened bymeans of a bolt or pin passing through the ends of the connector. Clevispin 207 and a cotter pin are used to fasten lower clevis fastener 203 tolink plate 204, which connection is further secured via backing/jam nuts212. See FIGS. 7A and 7C. As shown in FIGS. 7A and 7C, sensor cable 205is attached to upper clevis fastener 202 via load sensor pin 206. Sensorcable 205 and load sensor pin 206 are configured to measure and performload readings. Although shown in FIGS. 7A and 7B as a shortened cable,the sensor cable 205 is substantially long and extends up and into, fore.g. a strain indicator box on a deck, or to any other system orconfiguration that may convert measured load signals into direct modeload output readings. In exemplary embodiments, sensor cable 205 is 80feet long.

As shown in FIG. 7D, tension rod 201 b is secured to tension rod 201 cvia two backing/jam nuts 212 and sleeve nuts 209. Each backing/jam nut212 locks each sleeve nut 209 onto each rod 201 b 201 c to secure thetwo rods 201 b 201 c together. FIG. 7E shows an example embodiment of aconnection to secure tension rod 201 c to track system 300 that includesa backing/jam nut 212, clevis fastener 211, and clevis pin 210, whichconnection may be further secured via a cotter pin. In an exemplaryembodiment, as shown in FIG. 7F, clevis fastener 211 is fastened to agusset plate 302 attached to a longitudinal I-beam 301 of track system300. Particularly, clevis fastener 211 is placed over the gusset plate302 so that apertures in fastener 211 line up with an opening in gussetplate 302, such that it may be attached to gusset plate 302 via clevispin 207 and a cotter pin and further secured via a backing/jam nut 212.

FIG. 7G is a side close-up view of a hydraulic pre-tensioning ram 220attached to tension rod assembly 200 via hydraulic lines 221. In someembodiments, hydraulic pre-tensioning ram 220 may be installed withtension rod 201 a over deck fitting assembly 102. See FIG. 7G. Sincetension rod assembly 200 is attached to the I-beams 301 of track system300, a special pre-load must be applied to ensure the entire system 100stays in place during operation. To that end, a hydraulic pre-tensioningram 220 may be used to allow for/apply a simultaneous pre-load to eachI-beam 301. Pressure gauges may also be located on the deck thatcorrelate to real-time readings obtained from the sensor cables 205/loadsensor pin 206, and that are configured to measure the load within thevarious assemblies and overall system 100. In some embodiments, thereadings may also be obtained via a direct readout on a computer screenlocated on the deck. Pressure gauges may contain various pressurecontrol valve settings to control the pressure and estimated tensionload of the system 100. For example, a reading of 100 psi on a pressuregauge may show up to 1313 lbs of tension load, thus indicating to areader/user topside whether to increase or decrease the pressuresettings for the system 100 as needed. A reading of 400 psi on apressure gauge may show up to 5250 lbs of tension load. A reading of 800psi on a pressure gauge may show up to 10,500 lbs of tension load. Areading of 1150 psi on a pressure gauge may show up to 15,100 lbs oftension load. Finally, a reading of 1450 psi on a pressure gauge mayshow up to 19,000 lbs of tension load. Tension rod assembly 200 isconfigured to have a functional operating range of 0 to 75,000 lbs, butcomponents of the assembly 200 may withstand tension loads of 100,000lbs without yielding any structural degradation. In exemplaryembodiments, system 100, including a thruster and cradle 600, has a loadcapacity (dry condition) of 66,000 lbs. System 100, including a thrusterand cradle 600, also has an overload capacity (without yielding drycondition) of 80,000 lbs. Beam 301 tension loads are continuouslymeasured and monitored using the calibrated load cell instrumentationdescribed herein. In exemplary embodiments, this load cellinstrumentation can reliably operate at approximately 50 feet of waterdepth.

Referring to FIGS. 8A and 8B, top and bottom isometric views of tracksystem/beam track weldment 300 are shown. Track system 300 is configuredto be attached to the surface of a hull 101. In a particular embodiment,track system 300 is installed under and proximate to a bottom surface ofthe hull 101, parallel to a deck surface of the hull 101. See, e.g.,FIG. 3. Track system 300 includes two longitudinal I-beams 301 connectedtogether via stiffeners 304 305. Stiffeners 304 305 include lateralI-beam stiffeners 304 and/or angled I-beam stiffeners 305 configured toact as secondary tie beams or sections attached to the beams 301 tostiffen them against any deformations. Track system 300 further includesa gusset plate 302 installed on top of an end of each I-beam 301. SeeFIG. 8A. Each gusset plate 302 has openings 302 a configured forinsertion of connections to tension rod 201 c and/or tension rodassembly 200. Each longitudinal I-beam 301 may constitute one solidbeam. In other embodiments, each beam 301 may include multiplebeams/beam subassemblies attached to each other via bolting or otherattachment mechanisms. I-beams 301, I-beam stiffeners 304, 305, andgusset plates 302 may be attached to each other via fasteners, bolts, orany other mechanisms.

Track system 300 further includes a hoist rack 303 installed under/to alower flange of each I-beam 301. See FIG. 8B. In exemplary embodiments,hoist rack 303 is made of steel and welded to each I-beam 301. Hoistrack 303 is configured to assist a hoist system 400 to move/drive alongthe track system 300. Particularly, hoist rack 303 functions as a gearrack having teeth equally spaced along the rack 303 such that when apinion gear of a motor is placed on top of the rack 303, the linearnature of the rack 303 converts the pinion's rotary motion into linearmotion. Track system 300 is further configured such that the center oftrack system 300 has a substantially square shape to coincide withpositioning under thruster well opening, O, for removal and insertion ofa thruster. Track system 300 further includes thruster well positioningposts 308 on each I-beam 301 constituting part of the substantiallysquare shaped center of track system 300. Thruster well positioningposts 308 help guide, align, and install track system 300 to the hull101 by insertion and placement into sides of opening, O. See, e.g., FIG.4. Once positioned/secured within opening, O, posts 308 helpstabilize/keep in place the track system 300 during operation of thesystem 100. In an exemplary embodiment, thruster well positioning posts308 are square tubings made of steel.

Track system 300 includes triangular shaped plates 310 at an opposingend to the end having the gusset plates 302. See FIG. 8A. Triangularshaped plates 310 have openings 310 a, similar to openings 302 a ingusset plates 302, for insertion of connections to tension rod 201 cand/or tension rod assembly 200. In some embodiments, track system 300may include beam extensions 306 installed external and adjacent to thetriangular shaped plates 310 and configured for supporting floatationrigging to position track system 300 under the hull 101. In variousembodiments, beam extensions 306 may be attached to parachute lift bagsconfigured to lift and lower, and move from side to side, track system300 prior to installation under hull 101. In exemplary embodiments,parachute lift bags may be 10 foot diameter air bags. In exemplaryembodiments, I-beams 301, including beam extensions 306, have a totallength of approximately 742 inches, and a width of approximately 175inches. In other embodiments, I-beams 301 without beam extensions 306have a total length of 567 inches.

Since beams 301 are aligned and braced against a bottom surface of thehull 101, bottom surface of the hull 101 may have a flatness achieved byusing compliant rubber or wood dunnage strips corresponding to eachI-beam 301 at critical hull 101 locations. Load carrying I-beams 301 maybe sized to support thruster weight and support equipment with a SafetyFactor of +2.5. Corrosion resistant materials, epoxy coatings, and/orother protections may be used on the track system 300 where needed toprevent corrosion of the track system 300 while underwater. In variousembodiments, beams 301 may be fabricated from alloy steel or carbonfiber composite materials.

Referring to FIG. 9, an isometric view of a transfer frame 500 is shown.Transfer frame 500 includes multiple opposing beams and/or platesattached to each other via bolting or other attachment mechanisms toform a substantially square or rectangular shaped structure. However,transfer frame 500 may have any shape suitable to allow for attachmentof transfer frame 500 to a hoist system 400, as well as for attachmentto a cradle 600. In an exemplary embodiment, hoist system 400 attachesto transfer frame 500 at a center position, C. As shown in FIG. 9,transfer frame 500 includes multiple padeyes at its center position, C,for connection to the hoist system 400. However, transfer frame 500 mayhave any other attachment mechanism for connection to hoist system 400.Transfer frame 500 is designed for a Safety Factor of +2.5. End plates500 a of transfer frame 500 are configured to act as contact padlocations for placement of crane 600 onto transfer frame 500. Transferframe 500 further includes tip mass stabilizers 501 mounted on itssides. Tip mass stabilizers 501 are vertical rods configured to assisttransfer frame 500 and cradle 600, i.e., carriage 650 in maintainingproper balance and stability/prevent carriage 650 from tipping,particularly when a payload is placed on transfer frame 500.

FIGS. 10A, 10B, and 10C are front, side, and top views of a hoist system400 in a retracted position 400 b. FIGS. 10D, 10E, 10F, and 10G arefront, side, and bottom isometric views of hoist system 400 in anextended position 400 a. FIGS. 11A and 11B are bottom isometric, andside, views of another embodiment of hoist system 450. FIG. 12 is a topisometric close-up view of a transfer frame 500 attached to a tracksystem 300 via hoist system 400. Hoist system 400 is movably attached totrack system 300 at a first end and secured to transfer frame 500 at asecond end. Particularly, the connection at the first end includesmultiple structural plates 408 positioned on either side of I-beam 301and secured together via rods, as well as drive and lifting motors 402403 secured to the plate whereby the pinion gear of the drive motor 402interacts with the teeth of hoist rack 303 to facilitate horizontalmovement of hoist system 400. Hoist system 400 attaches to transferframe 500 at the second end via a lifting block structure. Lifting blockstructure includes multiple structural plates 404 attached to a blockand pin type arrangement 401 that pins into a center padeye lug oftransfer frame 500. See FIGS. 10A, 10B, and 12. However, lifting blockstructure (and hoist system 400) may be attached to transfer frame 500via any other attachment mechanisms. In exemplary embodiments, block andpin type arrangement 401 is clevis shaped. As shown in FIGS. 10B and10E, lifting block structure is a substantially rectangular shapedstructure. In other embodiments, lifting block structure and block andpin type arrangement 401 may have any other shape suitable forperforming their functions.

Hoist system 400 is driven via by pneumatic power. Particularly, drivemotor 402 and lifting motor 403 of hoist system 400 are connected topressurized air lines that are routed down across side of the hull 101from connections located topside/deck. Compressed air for the pneumaticpower may be provided via an air compressor or from a pressure storagevessel or air receiver (i.e., a storage tank containing pressurizedair). Drive motor 402 and lifting motor 403 may be manually controlledby control levers/valves/tethered control pendants 410 operated bydivers underwater. See FIG. 10D. However, drive motor 402 and liftingmotor 403 may be controlled remotely. In other embodiments, hoist system400 may be driven by hydraulic power, electrical power, or anycombination of pneumatic, hydraulic, and/or electrical power. Otherpower systems, as would be known by a person of ordinary skill in theart, may be used.

Drive motor 402 of hoist system 400 is configured to drive attachedtransfer frame 500 and/or carriage assembly 650 (once cradle 600 isinstalled), transversely along the track system 300 via the rack andpinion connection to hoist rack 303 of track system 300. Drive motor 402drives the pinion gear secured directly to the rack 303 back and forthhorizontally along track system 300. In an exemplary embodiment, hoistsystem 400 can drive transfer frame 500 and/or carriage 650 along tracksystem 300 approximately 25 feet.

Lifting motor 403 is configured to raise/lift and lower attachedtransfer frame 500 and/or carriage 650. Particularly, the lifting motor403 drives the lifting block structure of hoist system 400 up and down,which lifting block is connected to the second end of hoist system 400secured to transfer frame 500. In exemplary embodiments, hoist system400 includes chain link structures 405 that wrap around/mesh withsprockets located within structural plates 404 408 and are tied tolifting motor 403 to assist lifting motor 403 in raising and loweringthe lifting block structure. See FIGS. 10C to 10G. Chain link structures405 are configured to impart structural tension to the block. Inexemplary embodiments, lifting motor 403 is pneumatically actuated suchthat it rotates chain link structure 405, thereby facilitating raisingand lowering of lifting block structure, which then allows for raisingand lowering of transfer frame 500 and/or carriage 650. Hoist system 400may raise the transfer frame 500 and/or carriage 650 above its nominaltransfer height on command. In exemplary embodiments, hoist system 400lifting/lowering rates ranges from approximately 0.2 to 0.6 inches persecond. Once hoist system 400 is fully lowered, hoist system 400 is inan extended position 400 a. See FIG. 10D. Once hoist system 400 is fullyraised, hoist system 400 is in a retracted position 400 b. See FIG. 10A.In an exemplary embodiment, hoist system 400 may raise/lift and lowertransfer frame 500 and/or carriage 650 approximately 9 feet.

As shown in FIG. 10C, drive motor 402 and lifting motor 403 may bepositioned external to hoist system 400 i.e. facing outward fromtransfer system 100. Alternatively, drive motor 402 and lifting motor403 may face inward towards transfer system 100. In embodiments, drivemotor 402 and lifting motor 403 may be positioned together on one sideof hoist system 400. See, e.g., FIG. 10C. In other embodiments, each ofdrive motor 402 and lifting motor 403 may be positioned on either sideof hoist system 400. See, e.g., FIGS. 11A and 11B. FIGS. 11A and 11Bshow another embodiment of hoist system 450 where the connection totransfer frame 500 is a hook type connection. Alternatively, hoistsystem 450 may attached to transfer frame 500 via any other attachmentmeans. Hoist systems 400 450 may be rated for 1.2 times the weight of athruster lower gearbox. In exemplary embodiments, two hoist systems 400are used, one on each I-beam 301. See FIG. 12. However, more or lesshoist systems 400 450 may be used as needed.

FIG. 13 is an isometric view of a cradle 600. FIGS. 13A, 13B, 13C, and13D are additional fragmentary enlarged views of parts of the cradle600. FIG. 14 is an isometric view of cradle 600 resting in the transferframe 500. Cradle 600 is a substantially square or rectangular shapedstructure configured to be lowered and fit directly on/into a transferframe 500, and further, to securely hold/enclose a thruster 700 in placeduring removal and insertion of thruster 700 from hull 101. However,cradle 600 may have any other shape to correspond to a shape of transferframe 500 and/or securely hold/enclose a thruster 700. Cradle 600 has anopen top face for easy removal and insertion of thruster 700 from cradle600.

Cradle has a padeye-flange connection 601 at its corners to easily reston and stay in place on end plates 500 a of transfer frame 500 uponinsertion onto transfer frame 500. In an exemplary embodiment, thepadeye-flange connection 601 has a flat bottom surface 601 b configuredto rest on a flat top surface of end plates 500 a of transfer frame 500.See FIGS. 9, 13A, and 14. Padeyes 601 also include apertures 601 a toallow for easy raising and lowering of cradle 600 via rigging from acrane and/or other lifting/lowering device. Cradle 600 includes twoopposing kort nozzle saddle plates 602 positioned internally withincradle 600 such that outer surface of thruster 700 kort nozzle (i.e.large circular diameter around the propeller) may rest on kort nozzlesaddle plates 602. See FIGS. 13B and 13C. Kort nozzle saddle plates 602have a substantially curved shape to correspond to circular shape ofthruster propeller. Kort nozzle saddle plates 602 assist in keepingthruster 700 stable and prevent it from moving while raising andlowering cradle 600. Cradle 600 further includes a gear case saddleplate 603 positioned internally within cradle 600 between kort nozzlesaddle plates 602 such that outer surface of thruster 700 gear boxhousing may rest on gear box saddle plate 603. See FIGS. 13 and 13D.Gear box saddle plate 603 has a substantially curved shape to correspondto circular shape of thruster gear box. Gear box saddle plate 603supports and stabilizes gear case in back of thruster 700 duringthruster operations. Cradle 600 is designed for a Safety Factor of +2.5.In various embodiments, cradle 600 may be fabricated from alloy steel orcarbon fiber composite materials.

Once cradle 600 is fully lowered such that it securely rests on transferframe 500, drive motor 402 drives carriage/carriage assembly 650 alongtrack system 300 in direction, B, towards thruster well opening, O, tofacilitate removal of thruster 700 from hull 101. See FIG. 14. Loweringthe carriage 650 to extended position 400 a prior to moving carriage 650across track system 300 is critical because not doing so will causecarriage 650 to come into contact with hull 101 and damage carriage 650and/or hull 101. In an exemplary embodiment, carriage 650 will beapproximately 190 inches below the hull 101 while in the extendedposition 400 a. FIG. 15 shows the carriage 650 positioned under thrusterwell opening, O, with hoist system 400 in an extended position 400 a.Once directly under opening, O, lifting motor 403 drives carriage 650vertically towards and into opening, O, such that hoist system 400 is ina retracted position 400 b. See FIG. 16. In an exemplary embodiment,carriage 650 will be raised via hoist system 400 such that it isapproximately 139 inches below the hull 101 to arrive at retractedposition 400 b. In other embodiments, carriage 650 will be raised viahoist system 400 such that it is approximately 153 inches below the hull101 to arrive at retracted position 400 b.

Hoist system 400 raises the carriage 650 through opening, O, into athruster well under hull 101. Thruster well is an air filled habitatunder hull 101 where thruster 700 is located and where divers can safelyenter and remove/install connections to thruster 700 from within hull101. Particularly, divers in the thruster well may manually disconnectthruster 700 from its lifting/steering pipe to facilitate removal ofthruster 700. Thruster 700 is then lowered from thruster well opening,O, into the carriage 650. See FIG. 17. In embodiments, once thruster 700is inserted into the carriage 650, hoist system 400 may performprecision alignment/micro-positioning to ensure stability of thethruster 700 within the carriage 650. Precision alignment may beperformed via connections of hoist system 400 to topside/deck or viamanual control levers 410 operated by divers. Particularly, hoist system400 may lift and/or drive carriage 650 inside a transfer envelope(amount of travel (x, y)) to determine the optimal/correct position ofthe carriage 650/thruster 700 under the thruster well, and/or the bestposition to ensure safe removal of thruster 700 from under hull 101. Inexemplary embodiments, transfer envelope includes a travel of three tofour inches in the X and Y axis. See FIG. 17.

Lifting motor 403 then drives carriage 650 vertically down and away fromopening, O, such that hoist system 400 is back to the extended position400 a. See FIG. 18. Drive motor 402 then drives carriage 650horizontally along track system 300 in direction, C, towards (outboard)position at end of track system 300. See FIGS. 18 and 19. Oncepositioned at the end of the track system 300 located external to hull101, carriage 650 is raised via hoist system 400 to retracted position400 b to facilitate removal of cradle 600 and enclosed thruster 700.Cradle 600 and enclosed thruster 700 may then be raised from carriage650/system 100 in direction, D, via rigging from a crane or otherlifting/lowering device. See FIG. 20. In an exemplary embodiment, thecrane or any other lifting/lowering device lifts cradle 600 and/orenclosed thruster 700 via the padeyes 601 located at the corners of thecradle 600 described herein. See FIG. 13. Cradle 600 and enclosedthruster 700 may be lifted onto a waiting barge via a barge crane. Thecrane may be located on a ship deck or on a structure near the ship,e.g., a dock. Transfer system 100 may allow for the transfer ofthrusters 700 that are approximately 25 to 80 tons. Thruster 700 may bea retractable demountable thruster. In a particular embodiment, thruster700 is an azimuth or azimuthing thruster.

In embodiments of the present disclosure, a method for removing, andsubsequently reinserting, a thruster 700 from a hull 101 is shown. Themethod includes installing the transfer system 100 described herein tothe hull 101. The method further includes moving the carriage 650described herein, including the transfer frame 500 and cradle 600,across the track system 300 in a first direction, B, towards a positiondirectly under a thruster well opening, O, under the hull 101 via thehoist system 400 described herein. The method includes raising thecarriage 650 towards the opening, O, via the hoist system 400, loweringthe thruster 700 from inside the hull 101 (i.e., from the thruster well)through the opening, O, and into the carriage 650, lowering the carriage650 and enclosed thruster 700 down and away from the opening, O, via thehoist system 400, moving the carriage 650 and enclosed thruster 700payload across the track system 500 in an opposite direction, C, towardsan end of the track system 500, and removing the cradle 600 and enclosedthruster 700 from the transfer system 500 and onto an upper surface, fore.g., a deck, for further repair and/or replacement.

Once repaired and/or replaced, the cradle 600 and repaired/new thruster700 may be lowered via the crane or other lifting/lowering device, indirection A, onto the transfer frame 500. The method includes moving thecradle-transfer frame structure, i.e. carriage 650, and enclosedthruster 700 across the track system 300 in direction, B, towards theposition directly under the opening, O, of the hull 101 via the hoistsystem 400, raising the carriage 650 and enclosed thruster 700 towardsthe opening, O, via the hoist system 400, and raising the thruster 700from the carriage 650 towards and through the opening, O, and into athruster well for insertion into and within hull 101. Particularly,thruster 700 may be raised up to align with the disconnected steeringpipe, and divers may manually connect/bolt steering pipe and thruster700 together such that thruster 700 is fully installed within hull 101.

While the embodiments are described with reference to variousimplementations and exploitations, it will be understood that theseembodiments are illustrative and that the scope of the disclosures isnot limited to them. Many variations, modifications, additions, andimprovements are possible, including removing and replacing items otherthan thrusters. Further still, any steps described herein may be carriedout in any desired order, and any desired steps added or deleted.

What is claimed is:
 1. A transfer system, comprising: a deck fittingassembly configured to be mounted to a hull; a tension rod assemblysecured to the deck fitting assembly; a track system secured to thetension rod assembly; a transfer frame movably secured to the tracksystem via a hoist system; and a cradle removably secured to thetransfer frame, wherein the cradle and transfer frame are verticallymovable and horizontally traversable along the track system.
 2. Thesystem of claim 1, wherein the tension rod assembly includes threetension rods removably secured to each other.
 3. The system of claim 1,wherein the track system is attached to the hull.
 4. The system of claim3, wherein the track system is substantially horizontal and parallel toa deck surface of the hull.
 5. The system of claim 4, wherein the tracksystem includes a beam track assembly having two longitudinal I-beamsconnected together via I-beam stiffeners, a gusset plate installed ontop of each I-beam, and a hoist rack installed under each I-beam.
 6. Thesystem of claim 5, wherein the hoist system is movably attached to thehoist rack at a first end and to the transfer frame at a second end. 7.The system of claim 6, wherein the hoist system includes a drive motorconfigured to move the cradle and transfer frame along the track system,and a lifting motor configured to raise and lower the cradle andtransfer frame.
 8. The system of claim 1, wherein the cradle isremovable via a crane or other lifting device.
 9. The system of claim 1,wherein the cradle is configured to securely enclose a thruster.
 10. Thesystem of claim 9, wherein the thruster is a retractable demountablethruster.
 11. The system of claim 10, wherein the thruster is an azimuthor azimuthing thruster.
 12. The system of claim 1, wherein the deckfitting assembly includes a deck block mounted on a deck plate and asupport flange installed onto the deck block.
 13. The system of claim 1,further comprising a sensor cable and load sensor pin attached to thetension rod assembly, the sensor cable and load sensor pin configured tomeasure and perform load readings of any load supported by the tensionrod assembly.
 14. The system of claim 5, further comprising a hydraulicpre-tensioning ram attached to the tension rod assembly, the ramconfigured to apply a simultaneous pre-load to each I-beam, therebysecuring the system in place during operation.
 15. The system of claim7, wherein the hoist rack includes teeth equally spaced along the rack,the teeth configured to interact with a pinion gear of the drive motorand assist the hoist system in moving the cradle and transfer framealong the track system.
 16. The system of claim 15, wherein theattachment at the first end includes multiple first structural platespositioned on either side of each I-beam and secured together via rods,and the attachment at the second end includes a lifting block structurehaving multiple second structural plates attached to at least one of ablock and pin type and hook type arrangement.
 17. The system of claim16, wherein the hoist system includes chain link structures that wraparound and mesh with sprockets located within first and secondstructural plates and are tied to the lifting motor to assist thelifting motor in raising and lowering the lifting block structure. 18.The system of claim 17, wherein the hoist system is driven via at leastone of pneumatic, hydraulic, and electric power.
 19. The system of claim8, wherein the cradle includes padeye-flange connections havingapertures.
 20. The system of claim 19, wherein the cradle includes kortnozzle saddle plates positioned internally within the cradle such thatan outer surface of a thruster kort nozzle rests on the kort nozzlesaddle plates, and a gear case saddle plate positioned internally withinthe cradle such that an outer surface of a thruster gear box rests onthe gear box saddle plate.
 21. A method for removing a thruster from ahull, comprising: mounting a deck fitting assembly to the hull, whereina tension rod assembly is secured to the deck fitting assembly, a tracksystem is secured to the tension rod assembly, and a transfer frame ismovably secured to the track system via a hoist system; lowering andremovably securing a cradle to the transfer frame, wherein the cradleand transfer frame are vertically movable and horizontally traversablealong the track system; moving the cradle and transfer frame across thetrack system to a position directly under an opening in the hull via thehoist system; raising the cradle and transfer frame towards the openingvia the hoist system; lowering the thruster from inside the hull throughthe opening and into the cradle; lowering the cradle, transfer frame,and enclosed thruster away from the opening via the hoist system; movingthe cradle, transfer frame, and enclosed thruster across the tracksystem towards an end of the track system; and removing at least one ofthe cradle and enclosed thruster.
 22. The method of claim 21, whereinthe cradle and enclosed thruster are removed via a crane or otherlifting device.
 23. The method of claim 21, further comprising removingand replacing at least one of the enclosed thruster and a new thruster.24. The method of claim 23, wherein the track system includes a beamtrack assembly having two longitudinal I-beams connected together viaI-beam stiffeners, a gusset plate installed on top of each I-beam, and ahoist rack installed under each I-beam.
 25. The method of claim 24,wherein the hoist system is movably attached to the hoist rack.
 26. Themethod of claim 25, wherein the hoist system includes a drive motorconfigured to move the cradle and transfer frame along the track system,and a lifting motor configured to raise and lower the cradle andtransfer frame.